Alkaline treatment method for refining used oils

ABSTRACT

An alkaline treatment method for refining used oils, wherein (a) the used oils are distilled; (b) the resulting distillate is treated with an alkaline agent in the presence of a solvent selected from water, a monoalcohol, a polyalcohol and a mixture of said a alcohols, said alkaline agent being present in a percentage by weight, based on the weight of the distillate, equal to the product F×(IA+IS), where F is a multiplier between 2 and 50 and IA and IS are the acid value and the saponification value respectively of said distillate, at a temperatue of around 80-330° C. for 2-200 minutes; (c) the reaction medium is washed with water then decanted to recover the oily phase; and (d) said oily phase is distilled. The method is useful for producing refined oils having excellent properties in that they are odorless and nearly colorless and in that they have a very low chlorine, phosphorus and sillicon content.

This application is a 371 of PCT/ER96/00974 filed Jun. 21, 1996.

The present invention relates to a process for refining used oilsleading to refined oil products which can be re-used as base oils, fueloils, or in an oil refinery.

According to the present application, the expression <<used oils>>designates an oil or a mixture of oils in variable proportionsoriginating from various origins in particular from industrialapplications.

As this is well known, industrial or engine lubricant oils containvarious additives used to provide the required specific characteristicsfor the contemplated applications. These additives are either organic(known as <<ashless additives>>) or organometallic. Apart from theirspecific feature (e.g. anti-corrosion, anti-wear, anti-oxidant,dispersant . . . ) they are all characterized by an excellent solubilityin base oils (hydrocarbons with boiling points above 350° C.) a thermalstability as high as possible and a volatility as low as possible.

The lubricants which are discarded or used oils contain as impuritiessuch additives either intact or under the form of decomposedby-products, as well as sediments (wear particles from moving parts,airborne particles, carbon . . . ) and hydrocarbons which were notpresent in the original lubricant and which are undesirable. The latterare essentially gasoline and gas--oil fractions, oxidation products(e.g. organic acids) and pyrolysis products. The presence of thesevarious impurities is rendering particularly difficult the refining ofused oils.

In general, industrial used oils as above defined exhibit the typicalcharacteristics given in the following Table 1:

                  TABLE 1                                                         ______________________________________                                        Chlorine content (mg/kg)                                                                             150-2000                                               Phosphorus content (mg/kg)                                                                           300-1300                                               Silicon content (mg/kg)                                                                              8-80                                                   Colour (ASTM D 1500)  >8                                                      Odour (sensorial evaluation)                                                                        very strong                                             Water content (wt %)  0.2-1.2                                                 Sediments (wt %)      0.1-0.5                                                 Viscosity at 40° C. (mm.sup.2 /s)                                                             35-140                                                 Total Acid Number (TAN, mg KOH/g)                                                                   0.9-4.5                                                 Saponification Number (SN, mg KOH/g)                                                                 4-17                                                   ______________________________________                                    

In Table 1 above, the phosphorus and silicon contents were determined byplasma, the chlorine contents either by X-Fluorescence (above 50 mg/kg)or coulometry (below 50 mg/kg), the Total Acid Number through the NFT60112 French standard, the viscosity at 40° C. through the NFT 60110standard, the color through the ASTMD 1500 standard; the odour wastested by sensorial evaluation of the operator and the SaponificationNumber was determined by potentiometry.

In order to separate the various contaminants from used oils andespecially to improve their colour and odour, several physical and/orchemical separation methods as well as refining processes have beendeveloped in order to reclaim them and use them as base oils, fuel oilsor in an oil refinery.

When a base oil application is contemplated the colour must be very low(at least below 4 according to the ASTM D 1500 standard).

When a combustible application is considered, such as in industrialheating systems, they must be odour free and exhibit a low residualacidity (i.e. TAN below 0.2 mg KOH/g) and a low chlorine content, apotential source of atmospheric pollutants.

Last, when they are to be treated in oil refineries (catalytic crackingor hydrogenation) their phosphorus, silicon and chlorine contents mustbe very low to avoid catalyst poisoning or destruction (i.e. morespecifically a phosphorus content of less than 5 mg/kg, a chlorinecontent below 35 mg/kg) and a silicon content of less than 5 mg/kg).

Among the known physical separation methods for treating used oils, itcan be cited vacuum distillation, solvent precipitation with a solventsuch as propane or "deasphalting" and ultra filtration. They all show asignificant effectiveness to remove sediments and, to a certain extentdemetallize or clarify used oils. However such physical methods do notenable to remove all the impurities in the used oils. Thus, for example,distilled fractions still have a very strong odour, a significantacidity and do contain unacceptable proportions of volatil compounds,chlorine, phosphorus and silicon.

Among the known chemical separation methods for treating used oils; itcan be mentioned the methods involving an alkaline agent. However, mostof these processes, are aiming to facilitate the coagulation andsubsequently the separation of the sediments, and are essentiallydesigned to protect the behaviour of the equipment (distillation, andheat exchangers by reducing the fouling). Here again, the resulting oilproducts are inadequate to be used as base oils to formulate newlubricants. Thus, for example alkaline treatments applied to used oilsprior to their vacuum distillation, although they do reduce odour andacidity of the resulting oils, do not quantitatively remove undesirablecontaminants such as chlorine, in view of the operating conditions inwhich the alkaline agents are used. The used oils, pretreated throughone of the above mentioned processes can be further refined by highpressure catalytic hydrogenation, by concentrated sulfuric acidtreatment, by activated clay contacting or by combining the last twotreatments, and in some cases by a distillation after one of thesetreatments.

High pressure catalytic hydrogenation cannot however, be performedwithout a rapid catalyst deactivation if the processed oils are notessentially free of contaminants like phosphorus, chlorine and silicone.Other processes of treatment involving sulfuric acid and/or activatedclay generate acidic sludges and used clay which are raising disposalproblems.

The known used oils refining processes do not adequately perform orraise by-products disposal problems. There was therefore a chlorine andsilicone. Other processes of treatment involving sulfuric acid and/oractivated clay generate acidic sludges and used clay which are raisingdisposal problems.

As the state of the art as above mentioned it can be cited the followingpatents:

FR-A-2552098 which discloses a retreatment process of used oilscomprising the steps to eliminate water and the volatil constituents,then carrying out an alkaline treatment prior to the total vacuumdistillation during which the tarry fraction is separated.

FR-A-2302335 discloses a process for the treatment of used mineral oilswherein an "intense purification" of the oil to be treated is carriedout prior to hydrogenation step as the final step of the process.

FR-A-2152821 discloses a process for regenerating non-aqueous lubricantused for metal working (for example cold rolling) which comprises thestep to contact the lubricant with an alkaline hydroxyde in the presenceof an aliphatic monoalcohol, this step being preferably followed by amechanical separation to eliminate the resulting precipitate for exampleby filtration or centrifugation.

The known used oils refining processes do not adequately perform orraise by-products disposal problems. There was therefore a real need forthe development of a process leading, in a simple and economical way, torefined oils presenting the all desired properties and thuscharacteristics.

The subject of the present invention is thus an used oils refiningprocess giving rise to refined oils meeting the various quality andpurity requirements, this process being characterized by the followingsequence of well-determined steps consisting in:

a) carrying out the distillation of the used oils,

b) contacting the resulting distillate with an alkaline reactant in thepresence of a solvent selected from water, monoalcohols, polyalcoholsand a mixture thereof, the proportion of the alkaline reactant usedbeing, in weight % to the weight of the distillate, equal to F×(TAN+SN),F being a multiplying factor between 2 and 50, TAN and SN beingrespectively the Total Acid Number and the Saponification Number, thecontacting treatment being carried out at a temperature between 80° C.and 330° C. for a time between 2 and 200 minutes,

c) washing the reaction medium with water followed by settling torecover the oil phase, and

d) carrying out a distillation of the above oil phase.

The process according to the present invention is very versatile as itcan be adapted, concerning its operative conditions, to the qualityrequirements of the finished products. More specifically, the processaccording to the invention can be applied subsequently to one of thephysical and/or chemical separation methods or prior to any of therefining processes, mentioned above.

According to a specific embodiment of the process according to theinvention the distillation step (a) is first performed under atmosphericpressure, at a temperature comprised between about 130° C. and 180° C.to remove water and the heavy gasoline fractions. This distillation issubsequently performed under a reduced pressure of about 650 to 12000Pa, and at a temperature comprised between about 240° C. and 345° C. torecover a small quantity of gas-oil fraction and a much larger amount ofvacuum distillate, corresponding to more than 60% of the starting usedoils. Although the whole distillate can be processed in step (b)described above, it is preferable according to the invention to use onlythe major fraction of the distillate.

The above preliminary distillation step is of special importance as itenables to separate the near total amount of the tarry material.

The alkaline reactant used in step (b) of the process is either sodiumhydroxide or potassium hydroxide but never a mixture of both.Preferably, according to the invention, potassium hydroxide is used.Owing to the proportion of alkaline reactant added above mentioned, thepH of the reacting medium (distillate+alkaline solution) is above 8 andpreferably between 9.5 and 13.

When the solvent used in step (b) is water, then the alkaline reactantconcentration in the aqueous solution is preferably between 50 and 96%wt. A particularly attractive aqueous solution of the alkaline reactantis the potassium hydroxide/water eutectic combination (86.7/13.3).

The aqueous alkaline solution is first prepared and then added underpermanent agitation to the distillate obtained in step (a). Thissolution can be "solid" at ambient temperature as it is the case of thepotassium hydroxide/water eutectic (86.7/13.3) which is the preferredreactant. In that case, the solution "solid" turns into a low viscosityliquid at reaction temperature.

When the solvent used in step (b) is a monoalcohol, a polyalcohol or amixture thereof, the alcoholic solution used is preferably such that themole ratio solvent/alkaline reactant is between 2 and 20 and morespecifically between 2.5 and 5.

According to a preferred embodiment of the invention, the quantity ofalcohol or mixture of alcohols used must be sufficient to warrant in thereacting medium an alkaline reactant concentration close to saturation.

The monoalcohol or polyalcohol preferably contains 2 to 8 carbon atomsand more specifically 2 to 5.

Among the preferred monoalcohols according to the invention, thefollowing can be mentioned: ethanol, n-propanol, isopropanol, n-butanol,sec-butanol, tert-butanol, isobutanol, pentanols, hexanols and octanols.Among the preferred polyalcohols according to the invention, thefollowing can be mentioned: ethyleneglycol di- or tri-ethyleneglycol.According to the invention, it is preferable to select alcohols with aboiling point lower than the initial boiling point of the distillatebeing processed, and/or being highly water soluble, this making easiertheir further separation by water washing or distillation.

The reacting medium is preferably prepared either by dissolving thealkaline reactant into the alcohol, then injecting this solution intothe distillate to be processed or by mixing the hot distillate with thealcohol and then adding the alkaline reactant in the form of solidpellets.

According to a more specific embodiment of step (b) of the processaccording to the invention, when using as solvent an alcohol or amixture of alcohols, the alkaline treatment of the distillate isperformed at alcohol reflux provided evaporation losses can be avoided.

According to an other specific embodiment of step (b) of the processaccording to the invention, when the reaction temperature is high, andespecially when the solvent includes an alcohol with a normal boilingpoint inferior to the selected reaction temperature, the alkalinetreatment of the distillate with the alkaline reactant is performedunder a pressure between 10⁵ and 50×10⁵ Pa, preferably between 10⁵ and25×10⁵ Pa in order to avoid evaporation losses.

After completion of the alkaline treatment, the reacting medium iswashed at least once with about 1 to 15% water at a temperature betweenambient temperature and 100° C. This water washing operation or step (c)of the process according to the invention is essential to remove anyalkaline reactant in excess, the alcohol if used as a solvent and allwater soluble by-products resulting from the alkaline reactedcontaminants.

When the water washing operation is performed, only once, it normallyuses 10% water at a temperature of about 100° C.

However, according to a most preferred embodiment, the water washingoperation is performed in two successive steps. The first one involveswashing the reacting medium from step (b) with about 1 to 10% water andat a temperature as low as possible, between 20° C. and 90° C. Thesecond one consists, after settling, in washing again the reacted mediumwith 1% to 10% water at a temperature as high as possible and at leastidentical to that of the first water washing operation.

With respect to the first washing operation, the temperature mustpreferably be as low as possible in order to minimize hydrolysis butsufficient to lower the viscosity of the reacted medium from step (b)and warrant sufficient settleability.

By contrast, the temperature for the second washing operation must be ashigh as possible in order to perform a thorough elimination of theresidual alkaline reactant.

The total amount of water involved in this specific embodiment ispreferably between 5 and 15%.

According to a variante of this two steps water washing operation, thesecond washing step can be performed with a weak acidic aqueous solutionsuch as hydrochloric acid between 0.1 and 1 N.

After the washing and settling steps, the oil phase is subjected to thedistillation step (d), firstly at atmospheric pressure and at atemperature between 70° C. and 270° C. to eliminate the last traces ofsolvent and next under vacuum at a pressure between 650 Pa and 1350 Paand at a temperature between 210° C. and 375° C., this leading to arefined oil and a residue which amounts to less than 5% of the initialoil phase prior to distillation.

According to a variante of the process of the invention, the waterwashing step (c) of the oil phase can be followed by at least one of thefollowing treatments: high pressure catalytic hydrogenation, reactionwith a sulfonating agent and/or activated carbon or clay contacting.

The sulfonating agent is preferably either concentrated sulfuric acid orchlorosulfonic acid.

The activated clay is preferably a mineral clay of the silicoaluminatetype which has been activated by acid treatment.

When the oil phase is reacted with a sulfonating agent, this treatmentis preferably followed by a neutralization of the oil phase, theneutralizing agent being either the water from step (c) or preferably byaddition of an aqueous ammonia solution.

The refined oil or base oil produced according to the process of theinvention exhibits excellent physical and chemical characteristics. Itis odour free, slightly coloured with very low chlorine, phosphorus andsilicon contents.

The main characteristics of the refined oils produced according to theprocess of the invention are summarized below.

                  TABLE II                                                        ______________________________________                                        Chlorine content (mg/kg)                                                                            <35                                                     Phosphorus content (mg/kg)                                                                          <5                                                      Silicon content (mg/kg)                                                                             <5                                                      Colour (ASTM D 1500)  <3                                                      Odour (sensorial evaluation)                                                                        Very slight                                             Water content (wt %)  <0.01                                                   Sediments (wt %)      None                                                    Viscosity at 40° C. (mm.sup.2 /s)                                                            <85                                                     Total Acid Number (TAN, mg KOH/g)                                                                   <0.05                                                   Saponification Number (SN, mg KOH/g)                                                                <0.20                                                   ______________________________________                                    

Comparison between Tables I and II clearly demonstrates the efficiencyof the process according to the invention especially with respect to thereduction of the major contaminants of used oils.

The following examples will better illustrate the application of theprocess according to the invention, based on used oils having thecharacteristics shown on Table I.

EXAMPLES 1 AND 2

From used oils of various industrial origins a distillation was firstperformed under atmospheric pressure, then after raising thetemperature, under a pressure of about 1350 Pa, leading to the followingfractions.

                  TABLE III                                                       ______________________________________                                        Fraction                                                                            Pressure (Pa)                                                                            Temperature (° C.)                                                                  Proportion (wt %)                               ______________________________________                                        1     1.013 × 10.sup.5                                                                   130/180      7.5% (H.sub.2 O + gasoline)                     2      5300/10700                                                                              240/285      9% (gas-oil)                                    3     650/2000   285/345      65%                                             ______________________________________                                    

The residue was approximately 18.5 wt % and was essentially tarryproducts.

The major fraction (65 wt % of the total) had the followingcharacteristics:

                  TABLE IV                                                        ______________________________________                                        Chlorine content (mg/kg)                                                                            60                                                      Phosphorus content (mg/kg)                                                                          27                                                      Silicon content (mg/kg)                                                                             9                                                       Colour (ASTM D 1500)  6.5                                                     Odour (sensorial evaluation)                                                                        very strong                                             Water content (wt %)  <80                                                     Sediments (wt %)      None                                                    Viscosity at 40° C. (mm.sup.2 /s)                                                            31.24                                                   Total Acid Number (TAN, mg KOH/g)                                                                   0.26                                                    Saponification Number (SN, mg KOH/g)                                                                1.30                                                    ______________________________________                                    

A part of the distillate representing 65% was processed under theconditions shown on Table V with a 50 wt % potassium hydroxide solution,at 300° C. and 14×10⁵ Pa pressure. Another part of the same distillatewas processed with the potassium hydroxide/water eutectic (86.7/13.3),at 220° C. and 10⁵ Pa pressure. Following the alkaline treatment, thereacted medium was washed several times with water at about 90° C. inorder to remove the excess of the alkaline reactant and the variouswater soluble by-products resulting from the alkaline treatment.

After settling and separation, the oil phase was distilled underatmospheric pressure first, then under vacuum comprised between 650 and1350 Pa. 96% of the initial distillate was thus recovered.

The key characteristics of the two refined oils are also shown on TableV, from which it is evident that both alkaline treatments are leading torefine oils showing the same phosphorus, silicon and chlorine contents.

It must however be stressed that the pure potassium hydroxide requiredto achieve this result is 7.2 wt % i.e. 45 times the (TAN+SN)stoechiometry if a 50 wt % aqueous solution is used, but is only 0.47 wt% i.e. 3 times the stoechiometry when the eutectic was used.

It must be further added that, in that latter case, the reactiontemperature was only 220° C. instead of 300° C.

These two examples clearly establish a much higher reactivity of thepotassium hydroxide/water eutectic (86.7/13.3).

                  TABLE V                                                         ______________________________________                                        Operating conditions                                                          Temp       Time   KOH aqu. KOH   Results (mg/kg)                              Examples                                                                              ° C.                                                                          mn     sol    (dry) P    Si   Cl                               ______________________________________                                        1       300    30      50    7.2   1    <1   16                               2       220    30      86.7  0.47  1    <1   16                               ______________________________________                                    

EXAMPLES 3 TO 11

Using the same initial distillate fraction and the same operatingprocedure, as described in the above examples step (b) of the alkalinetreatment of the process according to the invention was performed atvarious temperatures between 175° C. and 300° C., during a period oftime between 10 and 60 minutes, using n-octanol as solvent, according tothe conditions described in Table VI below.

The amount of alkaline reactant used was, in all cases at leastequivalent to twice the (TAN+SN) stoechiometry and all tests were formedunder atmospheric pressure, except examples 10 and 11 performed under apressure of 10×10⁵ Pa.

It results from Table VI that, at the same temperature, potassiumhydroxide give rise to very satisfactory results in reducing thephosphorus, silicon and chlorine contents.

                                      TABLE VI                                    __________________________________________________________________________    Tempera-                                                                             mn           ALKALINE    RESULTS                                       ture   Time                                                                             ALCOHOL   REACTANT    (mg/kg)                                       Ex                                                                              ° C.                                                                        mn Type  Mass %                                                                            NaOH (pure)                                                                         KOH (pure)                                                                          P Si                                                                              Cl                                        __________________________________________________________________________    3 175  10 n-C.sub.8 H.sub.17 OH                                                               4.4 --    0.49  5 2 32                                        4 200  60 n-C.sub.8 H.sub.17 OH                                                               3.24                                                                              --    0.36  3 <1                                                                              10                                        5 200  60 n-C.sub.8 H.sub.17 OH                                                               7.1 --    0.76  1 <1                                                                              8                                         6 200  60 n-C.sub.8 H.sub.17 OH                                                               19.9                                                                              --    2.14  1 <1                                                                              3                                         7 200  60 n-C.sub.8 H.sub.17 OH                                                               3.24                                                                              0.36  --    2 <1                                                                              18                                        8 200  60 n-C.sub.8 H.sub.17 OH                                                               7.1 0.79  --    2 <1                                                                              14                                        9 200  60 n-C.sub.8 H.sub.17 OH                                                               19.3                                                                              2.14  --    1 <1                                                                              12                                        10                                                                              250  30 n-C.sub.8 H.sub.17 OH                                                               7.7 --    1.29  1 <1                                                                              20                                        11                                                                              300  60 n-C.sub.8 H.sub.17 OH                                                               7.2 --    0.79  1 1 5                                         __________________________________________________________________________

EXAMPLE 12

According to the procedure described above, a distillation was performedon used oils from various origins, leading to a distillate with thefollowing characteristics:

    ______________________________________                                        Chlorine content (mg/kg)                                                                             72                                                     Phosphorus content (mg/kg)                                                                           18                                                     Silicon content (mg/kg)                                                                              23                                                     Colour (ASTM D 1500)   7                                                      Total Acid Number (TAN; mg KOH/g)                                                                    0.49                                                   Saponification Number (SN; mg KOH/g)                                                                 2.90                                                   ______________________________________                                    

One half of this distillate was processed with 2.5 wt % potassiumhydroxide at 85 wt % concentration (i.e. 2 wt % dry potassiumhydroxide), while the other half was processed with 4.71 wt % potassiumhydroxide at 85 wt % concentration (i.e. 4 wt % dry potassiumhydroxide). Both treatments were performed at 250° C. for about 30minutes.

The first half, processed with 2 wt % dry potassium hydroxide, wasdivided in two equal parts.

The first one was subjected to one water washing with 10% water at 100°C. and the second one to the following two water washing operations:

1) a first washing with 5% water at 65° C., and after settling; to

2) a second washing with 5% water at 100° C.

In a similar way, the second half, processed with 4 wt % dry potassiumhydroxide, was divided in two equal parts.

The first one was subjected to one water washing with 10% water at 100°C. and the second one to the following two water washing operations:

1) a first washing with 5% water at 65° C., and after settling; to

2) second wash with 5% water at 100° C.

After settling, each of the four oil phases collected was vacuumfractionated under a pressure of 1300 Pa in order to obtain for each oilphase the following four fractions.

    ______________________________________                                        Fraction I         264° C.-370° C.                              Fraction II        370° C.-441° C.                              Fraction III       441° C.-475° C.                              Fraction IV        475° C.-558° C.                              ______________________________________                                    

Colour determination of the above fractions was then carried outaccording to ASTM D 1500 and the corresponding results are summarized inthe following Table VII:

                  TABLE VII                                                       ______________________________________                                        Dry KOH                                                                       (wt %)    2%              4%                                                  Fractions I      II     III  IV   I    II  III  IV                            ______________________________________                                        Water  One    2.1    1.5  <2.5 <3.5 1.5  <3  <4   <6                          Washing                                                                              step                                                                          Two    <1.5   <1.5 <1.5 <3.5 <1   <1  <1.5 3.5                                steps                                                                  ______________________________________                                    

These data are clearly showing that the two steps water washingtechnique does lead to refined oils with superior colourcharacteristics, a result which was totally unexpected.

In addition, it has been determined that in order to maximize the oilphase yields prior to distillation, it was suitable, in the processinvolving two washing steps, to use for the first water washing a wateramount superior or equal to 2% but inferior or equal to 10%, andpreferably between about 4% and 6% which would warrant yields between90% and 98%.

I claim:
 1. A process for refining used oils containing variouscontaminants comprising the following sequence of steps consistingof:(a) fractionally distilling used oils and recovering a major fractionof the distillate, said distilling being first performed underatmospheric pressure at a temperature between about 130° C. and 180° C.and then under reduced pressure of about 650 to 12,000 Pa and at atemperature between about 240° C. and 345° C., (b) contacting the majorfraction of the distillate with an alkaline reactant selected from thegroup consisting of sodium hydroxide and potassium hydroxide in thepresence of a solvent selected from water, monoalcohols, polyalcoholsand a mixture thereof, the proportion of sodium hydroxide or potassiumhydroxide used being in weight percent to the weight percent of themajor fraction of the distillate equal to F×(TAN+SN), F being amultiplying factor between 2 and 50, TAN and SN being respectively theTotal Acid Number and Saponification Number of the distillate, saidcontacting being carried out at a temperature between 80° C. and 330° C.for a time between 2 and 200 minutes, (c) washing the product of step(b) with 1 to 15% water, followed by settling to recover an oil phase,and (d) fractionally distilling said oil phase under vacuum of about 650to 1,350 Pa and at a temperature between 210° C. and 375° C., in orderto recover the refined oil fraction.
 2. The process according to claim1, wherein step (c) is performed at a temperature in the range ofambient temperature to 100° C.
 3. The process according to claim 1wherein the alkaline reactant is potassium hydroxide.
 4. The processaccording to claim 1 wherein the solvent is water and the alkalinereactant concentration is comprised between 50% and 96% wt based to theweight of the aqueous solution.
 5. The process according to claim 1wherein the alkaline reactant is in the form of potassiumhydroxide/water eutectic (86.7/13.3).
 6. The process according to claim1 wherein the solvent is selected from monoalcohols, polyalcohols or amixture thereof, the alcoholic alkaline solution being such that themole ratio between the monoalcohol or the polyalcohol to the alkalinereactant is between 2 and
 20. 7. The process according to claim 6wherein the mole ratio between the monoalcohol or the polyalcohol to thealkaline reactant is between 2.5 and
 5. 8. The process according toclaim 1 wherein the monoalcohol or the polyalcohol contains 2 to 8carbon atoms.
 9. The process according to any of the above claimswherein step (c) of water washing is performed in two separate steps,the first one using 1% to 10% water at a temperature between 20° C. and90° C., and the second one involving, after settling, 1% to 10% water athigh temperature as high as possible and at least equal to thetemperature of the first step.
 10. The process according to claim 9wherein the second washing step is performed with a weak acidic aqueoussolution.
 11. The process according to claim 1 wherein the oil phasecollected from the washing step (c) is further processed by at least oneof the following processes: high pressure catalytic hydrogenation,reaction with a sulfonating agent or contacting with activated carbon orclay.
 12. The process according to claim 11 wherein the sulfonatingagent is either concentrated sulfuric acid or chlorosulfonic acid. 13.The process according to claim 11 wherein the activated clay is an acidtreated silicoaluminate.
 14. The process according to claim 11 whereinthe oil phase after being reacted with a sulfonating agent is thenneutralized.
 15. The process according to claim 14 wherein the oil phaseis neutralized by an aqueous ammonia solution.